1. Field of the Invention
The present invention relates to a relative position and/or posture measuring system including a magnetic field generator including a plurality of transmission coils arrayed orthogonal to each other for transmitting a magnetic signal from each transmission coil, a magnetic field detector for receiving a magnetic field generated in each transmission coil as a magnetic field detection value for each transmission coil, and a computing unit for computing a relative distance and a relative posture between the magnetic field generator and the magnetic field detector based on the magnetic field detection value for each transmission coil received by the magnetic field detector.
2. Description of Related Art
There has been known the Polhemus sensor using a magnetic sensor as a system for measuring a space position of an object to be measured or a posture thereof in the measuring step.
This polhemus sensor is a system for grasping a space position of an object to be measured and a posture thereof defined by the Euler angle by positioning a magnetic field generator including three transmission coils orthogonal to each other at an origin of a measurement space, also providing a magnetic field detector including three receiving coils orthogonal to each other corresponding to the three transmission coils respectively, detecting a magnetic field generated when a driving current is loaded to the transmission coils with the receiving coils, and processing the detected magnetic field with a computing unit.
More specifically, a driving current is loaded to the three transmission coils in the time division mode to drive the transmission coils sequentially, three magnetic fields received by the receiving coils when each transmission coil is being driven are detected, and a simultaneous equation is set based on totally 9 signal values to compute X-, Y-, Z-axial positions of an object to be measured, a pitch, yaw, and roll angles of the object to be measured (Refer to, for instance, Reference: U.S. Pat. No. 4,017,858, specification, column 10 to column 12, FIG. 10 and FIG. 11).
With the polhemus sensor as described above, not only a three-dimensional space position of an object to be measured, but a posture thereof at the time point can be grasped, and therefore by attaching the polhemus sensor to a head-mount display unit connected to a computer, and when an operator puts on this head-mount display unit, a screen to be displayed on the head-mount display can be changed in response to movements of the operator such as looking back or moving forward or backward, and thus utilization of the polhemus sensor as a position measuring system in virtual reality is highly expected.
The polhemus sensor as disclosed in the Reference has, however, the following problems.
In other words, generation of a magnetic field by each transmission coil is carried out in the time division mode, a long period of time is required for detecting a position and a posture of an object to be measured, and the rate action is disadvantageously delayed.
Further, the communication system using a carrier wave as it is employed, so that the system is weak to noises, and detection of a position is possible within a short distance, and therefore the communication system can not practically be applied as a position measuring system in the virtual reality. Especially, when the number of channel is increased for more accurately computing a state of the object to be measured, influence by noises becomes disadvantageously larger.